--- a/toolkit/mozapps/extensions/test/browser/head.js
+++ b/toolkit/mozapps/extensions/test/browser/head.js
@@ -47,17 +47,18 @@ const PREF_STRICT_COMPAT = "extensions.s
 var PREF_CHECK_COMPATIBILITY;
 (function() {
   var channel = "default";
   try {
     channel = Services.prefs.getCharPref("app.update.channel");
   } catch (e) { }
   if (channel != "aurora" &&
     channel != "beta" &&
-    channel != "release") {
+    channel != "release" &&
+    channel != "esr") {
     var version = "nightly";
   } else {
     version = Services.appinfo.version.replace(/^([^\.]+\.[0-9]+[a-z]*).*/gi, "$1");
   }
   PREF_CHECK_COMPATIBILITY = "extensions.checkCompatibility." + version;
 })();
 
 var gPendingTests = [];